An image forming apparatus contains an image forming section; a fixing unit configured to heat the toner image by a heater to fix on the sheet; a power source section; an acquisition section configured to acquire a voltage value of the input power source; a sensor configured to detect a temperature of the fixing unit; and a controller configured to control the heater to stabilize the temperature at a first temperature upon acquiring a first voltage value as the voltage value by the acquisition section, and configured to control the heater to stabilize the temperature at a second temperature upon acquiring a second voltage value as the voltage value by the acquisition section, the first voltage value being lower than the second voltage value, the first temperature being higher than the second temperature.